This invention relates to a plural beam cathode ray tube electron generating assembly and more particularly, to improved means for supporting shielded cathode assemblies in a multiple beam in-line electron gun construction.
In certain types of multiple gun cathode ray tube electron generating assemblies, wherein the guns are oriented in an in-line arrangement, it has been conventional practice to support the individual cathodes in annular ceramic discs which, in turn are concentrically positioned and retained within the cylinder of the respective cup-like control electrodes. It has been found that ceramic-supported cathodes evidence certain shortcomings relating to emission characteristics and manufacturability. Exact positioning of the cathode-to-control electrode spacing is difficult to consistently achieve and maintain by the conventional retaining means. Since the ceramics are formed as annular elements, wherein the individual cathodes are affixed by swage bead-like formations, engaging the upper and lower surfaces of the discs, there is a structurally dictated minimum to which the diameter of the apertured ceramic may be reduced. Thus, miniaturization of electron gun assemblies employing ceramic means for supporting the cathodes is limited by the required dimensioning of the ceramic support elements incorporated therein. Furthermore, such construction does not readily lend itself to the utilization of shielded cathode assemblies within the control electrode cup-like structures.